Guide Vane for a Variable Turbine Geometry

ABSTRACT

A guide vane, particularly for a turbocharger, has a line of curvature with at least one or more sectors having a discontinuous course.

The invention relates to a guide vane for a variable turbine geometry of a turbocharger.

A turbocharger generally consists of an exhaust gas turbine in the exhaust gas flow, said exhaust gas turbine being connected to a compressor in the induction tract. In this arrangement the turbine is set into rotation by the exhaust gas flow of the engine and thereby drives the compressor. In the process the pressure in the induction tract of the engine is increased via the compressor with the result that during the induction stroke a greater volume of air reaches the cylinder than in the case of a naturally aspirated engine. In this way more oxygen is available for combusting a commensurately greater amount of fuel.

With conventional turbochargers the boost pressure is limited when necessary such that some of the hot exhaust gas is conducted past the turbine by means of a diverter valve or, as the case may be, a bypass or wastegate, thereby reducing the output power of the turbine. To compensate for this the turbine is dimensioned sufficiently large such that it operates efficiently even at well below the nominal operating point of the engine.

Also known from the prior art are turbochargers which are provided with a variable turbine geometry VTG in order to be able to adapt the power delivery and the response characteristics to different operating conditions, such as load cycle changes for example. In order to achieve this, adjustable, non-rotating guide vanes are disposed in the turbine inlet or in the turbine housing. With the guide vane in the closed position, high circumferential components of the flow velocity and a high enthalpy gradient lead to a high turbine output and hence to a high boost pressure. In the fully open position of the guide vanes, the maximum throughput of the turbine is developed with a high centripetal component of the velocity vector of the flow. The advantage of this type of power regulation compared to regulation by means of a bypass resides in the fact that the full exhaust gas mass flow is ducted across the turbine at all times and used for the power conversion.

As far as the variable turbine geometry is concerned, the shape of the vane profile is the main influencing factor with regard to thermodynamic efficiency, the control characteristics and the requisite radial installation space.

The most disparate shapes for the profile of the adjustable blade exist in the prior art. In general the aim is to combine an optimum of efficiency, control characteristics and the smallest possible reference circle (installation space). Usually the shape is described via the line of curvature that runs between the center point of the head radius and the center point of the end radius of the adjustable blade. Said line of curvature is produced in that tangential circles are assumed within the profile on the top and bottom sides. In this case the line connecting the centers of the circles describes the line of curvature.

In this case there are purely straight or curved variants or variants composed of both possibilities. A common aspect of all said variants is that the lines of curvature possess a continuous shape or course, i.e. the individual curve segments transition tangentially into one another. In other words the line of curvature has no bend or kink.

Accordingly it is the object of the present invention to provide an improved guide vane geometry for a turbocharger having a variable turbine geometry.

This object is achieved by means of a guide vane having the features recited in claim 1.

Accordingly the invention provides a guide vane, in particular for a turbocharger, wherein the line of curvature of the guide vane has at least one or more than one sector having a discontinuous course.

The guide vane is particularly advantageous in the embodiment of a flow profile. In this case the degree of efficiency can be improved while control characteristics and installation space requirements remain unchanged.

Advantageous embodiments and developments of the invention will emerge from the dependent claims as well as from the description with reference to the drawings.

In one embodiment variant according to the invention, the line of curvature has at least one sector having two sections which are connected to each other, the two sections transitioning into each other discontinuously or, as the case may be, non-tangentially at their point of connection. In other words, the sections form a kink or bend at their connecting point. This has the advantage that by means of such an embodiment of the guide vane, in the case of a variable turbine geometry for example, the efficiency of a turbocharger can be improved.

In another embodiment variant according to the invention, in addition to at least one sector having a bend or, as the case may be, having a non-tangential transition between two sections, the line of curvature of the guide vane has at least one sector whose two sections transition into each other continuously or, as the case may be, tangentially at their connecting point. In this way the line of curvature of a guide vane can be varied in any suitable way with continuously and discontinuously running sectors, according to which flow profile is to be achieved.

According to another inventive embodiment variant, at least one, more than one or all sections of the line of curvature are identical or different in respect, for example, of their shape, position and/or dimensions. This applies analogously to the sectors of the line of curvature that are formed by the sections. Thus, the most disparate designs of guide vanes can be implemented, all of which have at least one sector having a discontinuous course.

In yet another embodiment variant according to the invention, the guide vane consists for example of four sections, wherein the first and second sections form a first sector having a continuous course. A second sector is formed by the second section and a third section, wherein the second and third sections transition discontinuously into each other or, as the case may be, form a bend at their connecting point. A third sector, consisting of the third section and a fourth section, again has a continuous course. Such a guide vane represents an example in which the line of curvature has a bend. In this case both or at least one of the sections of the first and third sectors can for example be curved upward or, as the case may be, downward.

In another embodiment variant according to the invention, the sections of which the line of curvature is composed can be embodied for example as arc-shaped or straight. In this case the sections can be curved upward or downward or, if the sections are straight, they can be oriented for example horizontally, vertically, or diagonally upward or diagonally downward. The sections can in this case be arbitrarily combined with one another, with at least one sector which is formed by means of the sections having a discontinuous course. In this way a multiplicity of flow profiles can be realized, according to the desired function or desired application.

The invention is explained in more detail below with reference to the exemplary embodiments depicted in the schematic figures of the drawings, in which:

FIG. 1 shows a first embodiment variant of a guide vane according to the prior art;

FIG. 2 shows a second embodiment variant of a guide vane according to the prior art;

FIG. 3 shows a third embodiment variant of a guide vane according to the prior art;

FIG. 4 shows a first embodiment variant of a guide vane according to the invention; and

FIG. 5 shows a second embodiment variant of a guide vane according to the invention.

In the figures the same reference signs designate identical or functionally identical components, unless explicitly stated to the contrary.

FIG. 1 shows a first embodiment variant of a guide vane 10 according to the prior art. The guide vane 10 is drawn therein in a diagram, the diagram having an x-axis and a y-axis. This representation applies to all guide vanes 10 as shown in FIGS. 1 to 5.

As described hereintofore, the shape of a guide vane 10 is normally described by way of the line of curvature 12 which runs between the center point 14 of the head radius and the center point 16 of the end radius of the guide vane 10. This line of curvature 12 is produced in that tangential circles are assumed within the profile of the guide vane 10 on the top and bottom sides 18, 20 respectively. In this case the connecting line between the center points of the circles describes the line of curvature 12.

In the present case, as shown in FIG. 1, the line of curvature 12 runs in a wave shape. In this case the line of curvature 12 is composed of four sections a1 to a4. The first and second section a1, a2, which form a first sector b1, are therein embodied in each case curved upward in an arc shape, the two sections a1, a2 of the line of curvature 12 tangentially transitioning into each other at their connecting point 22. In this case the sector b1 forms a continuous course without a bend. Furthermore the third section a3 is likewise embodied as arc-shaped, being curved downward, in contrast to the first and second sections a1, a2. The second and third sections a2, a3 likewise transition into each other tangentially at their connecting point 22, such that the second sector b2, which is formed from the second and third sections a2, a3, has a continuous course. This also applies analogously to the third sector b3. This is formed from the third section a3 and a fourth section a4, both sections a3, a4 being embodied in an arc shape and being curved downward. The two sections a3, a4 of the line of curvature 12 transition tangentially into each other at their connecting point 22, i.e. the sector b3 has a continuous course, without a bend being produced at the transition 22 between the two sections a3, a4. All three sectors b1 to b3 run above the x-axis in the diagram in FIG. 1, the first sector b1 furthermore being significantly longer and more strongly curved than the third sector b3.

In the second embodiment variant of a guide vane 10 according to the prior art, as shown in FIG. 2, the line of curvature 12 is likewise composed of four sections a1 to a4. The line of curvature 12 in this case runs above the x-axis, initially rising in an upward curve before slowly dropping away toward the other end.

The first section a1 of the line of curvature 12 is in this case curved downward in an arc shape, while the directly adjoining section a2 is curved upward in an arc shape. The two sections a1 and a2 transition tangentially into each other at their connecting point 22 such that the first sector b1, which is formed by the first and second sections a1, a2, has a continuous course. The second sector b2, which is composed of the second section a2 and a third section a3, likewise has a continuous course. Thus, the third section a3 is likewise curved upward in an arc shape, it and the second section a2 transitioning tangentially into each other at their connecting point 22, without a bend being produced in the process. The third sector b3 of the line of curvature 12 is formed from the third section a3 and a fourth section a4. The fourth section a4 is in this case curved downward in an arc shape, the third and fourth sections a3, a4 transitioning tangentially into each other at their connecting point 22.

FIG. 3 shows a third embodiment variant of a guide vane shape likewise according to the prior art. In this case the guide vane 10 consists, as in the first and second embodiment variants, of four sections a1 to a4. The line of curvature 12 runs in this case in a wave shape initially in an arc above the x-axis and then in an arc below the x-axis.

The first and second sections a1, a2 of the line of curvature 12 are embodied in an arc shape and run in an upward curve. The two first and second sections a1, a2 transition tangentially into each other at their connecting point 22. The second sector b2 of the line of curvature 12 is formed by the second section a2 and a third section a3. The third section a3 is likewise embodied in an arc shape and curved downward. In this case the two sections a2 and a3 transition tangentially into each other at their connecting point 22, such that no sharp bend is produced in this sector. The fourth sector b4 is likewise formed by the third section a3 and a fourth section a4. The fourth section a4 is likewise embodied curved downward in an arc shape. In the area of their connecting point 22 the third and fourth sections a3, a4 transition tangentially into each other. The sectors b1 to b4 or, as the case may be, the line of curvature 12 thus form a continuous course overall, in the same way as the two other previously described embodiment variants of a guide vane 10 according to the prior art.

FIG. 4, in contrast, shows a first embodiment variant of a guide vane 10 according to the invention. In this case the guide vane 10 consists, for example, of four sections a1 to a4. A first sector, consisting of the first and second sections a1, a2, in this case has a continuous course. The first and second sections a1, a2 are in this case embodied in an arc shape and curved upward. At their connecting section or connecting point 22 the first section a1 transitions tangentially into the second section a2, such that a continuous course is produced without a bend or kink. A second sector b2 is formed by the second section a2 and a third section a3, the second and third section a2, a3 in each case being embodied in an arc shape and being curved upward. In this instance, however, the sections a2 and a3 do not transition tangentially into each other at their connecting point 22, but instead form a bend 24. For this purpose the second sector b2, rather than forming a continuous course as in the prior art, forms a discontinuous course or, as the case may be, has a sharp bend 24 at the connecting point 22 of the two sections a2, a3. The third sector b3 consists of the third section a3 and a fourth section a4 and in this case forms a continuous course. The fourth section a4 is in this case embodied in an arc shape and curved upward. The third and fourth sections a3, a4 transition tangentially at their connecting point 22. This means that in the present example the guide vane 10 has a sector b2 having a discontinuous course of the line of curvature 12 in which the second and third section a2, a3 form a type of bend 24 at their connecting point 22 or, as the case may be, do not transition tangentially into each other. The other sectors b1 and b3, in contrast, have a continuous course of the line of curvature 12, without one of the sectors in this case embodying a bend.

In the present case the line of curvature 12 forms two arcs, firstly an arc that curves upward and is formed from the sections a1 and a2, and, in comparison therewith, a further arc having a very much flatter curve and consisting of the sections a3 and a4. The two arcs form the bend 24 at their connecting point 22.

FIG. 5 furthermore shows a second embodiment variant of a guide vane 10 according to the invention. The line of curvature 12 of the guide vane 10 in this case consists of four sections a1 to a4. The first and second section a1, a2 are in this case embodied in an arc shape and curved upward. The first and second sections a1, a2 transition tangentially into each other at their connecting point 22 such that the sector b1, which is formed from the two sections a1, a2, has a continuous course. The second sector b2 is formed from the second section a2 and a third section a3, the third section a3 likewise being curved upward. In contrast, the two sections a2, a3 do not transition tangentially into each other at their connecting point 22, but instead form a type of bend 24, as shown in FIG. 5. Accordingly the second sector b2 has a discontinuous course. The third sector b3, which is formed from the third section a3 and a fourth section a4, again has a continuous course. The two third and fourth sections a3, a4 are in this case embodied in an arc shape and are curved upward. They transition tangentially into each other at their connecting point 22. Thus, the line of curvature 12 of the guide vane 10 according to the invention has a discontinuous course at least in the sector b2, while the two other sectors b1 and b3 have a continuous course without a bend being formed. In contrast to the first embodiment variant of the invention, in the second embodiment variant of the invention the first sector b1 is embodied as longer or, as the case may be, the arc spanned from the sections a1 and a2. The third sector b3 or, as the case may be, the arc spanned from the sections a3 and a4 is in return shorter in the second embodiment variant than in the case of the first embodiment variant.

Although the present invention has been described hereinbefore with reference to two preferred exemplary embodiments, it is not restricted thereto, but can be modified in a multiplicity of different ways. In particular it is also conceivable that, instead of arc-shaped sections, sections having for example a straight shape (not shown) can be combined with one another and/or with the arc-shaped sections, according, for example, to the desired flow profile of the respective guide vane. Furthermore, a guide vane can have at least one sector consisting of two sections or a multiplicity of sectors or sections, for example two, three, four, five, six and more sectors or sections. At the same time sections having an arbitrary shape, arrangement and/or arbitrary dimensions can be combined with one another. This also applies analogously to the sectors which are formed from the sections. In the two inventive embodiment variants, as shown in FIGS. 4 and 5, the sectors b1 to b3 are in each case arranged substantially above the x-axis in the diagrams. In principle the sectors or, as the case may be, sections of the line of curvature 12 can run arbitrarily, for example at least in part below the x-axis, as shown for example in FIG. 3 with reference to the prior art. Optionally the sectors or, as the case may be, sections of the line of curvature 12 can also run completely below or in part on the x-axis. Furthermore, straight and arc-shaped sections can be varied arbitrarily along the line of curvature 12 of a guide vane 10. In principle the guide vane 10 can in this case have at least one bend 24 or a multiplicity of bends 24 or, as the case may be, points at which the individual curve segments of the line of curvature 12 do not transition tangentially into one another. For example, the line of curvature 12 can have one, two, three, four or more of these so-called kinks or bends 24 or, as the case may be, non-tangential transitions, wherein the bends 24 can be provided at arbitrary positions on the line of curvature 12, according to function or application. 

1-10. (canceled)
 11. A guide vane, comprising: a line of curvature including sectors; at least one or more of said sectors having a discontinuous course.
 12. The guide vane according to claim 11, wherein said line of curvature includes at least one of said sectors having two sections connected to each other, said two sections transitioning into each other discontinuously or non-tangentially at a connecting point.
 13. The guide vane according to claim 11, wherein said line of curvature includes at least one of said sectors having two sections connected to each other, said two sections transitioning into each other continuously or tangentially at a connecting point.
 14. The guide vane according to claim 12, wherein at least one, more than one or all of said sections each have at least one of the same shape, a different shape or the same or different dimensions.
 15. The guide vane according to claim 13, wherein at least one, more than one or all of said sections each have at least one of the same shape, a different shape or the same or different dimensions.
 16. The guide vane according to claim 12, wherein at least one, more than one or all of said sectors each have at least one of the same shape, a different shape or the same or different dimensions.
 17. The guide vane according to claim 13, wherein at least one, more than one or all of said sectors each have at least one of the same shape, a different shape or the same or different dimensions.
 18. The guide vane according to claim 11, which further comprises: first, second, third and fourth sections; said sectors including first, second and third sectors; said first sector being formed by said first and second sections transitioning continuously into each other at a connecting point; said second sector being formed by said second and third sections transitioning discontinuously into each other at a connecting point; and said third sector being formed by said third and fourth sections transitioning continuously into each other at a connecting point.
 19. The guide vane according to claim 18, wherein said second and third sections of said second sector form a bend therebetween at said connecting point.
 20. The guide vane according to claim 18, wherein said first and third sectors are each curved upward or downward, or one of said first and third sectors is curved upward and the other is curved downward.
 21. The guide vane according to claim 11, wherein at least one of said sections of a sector is arcuate or straight and is curved or oriented upward or downward.
 22. The guide vane according to claim 11, wherein the guide vane is a turbocharger guide vane.
 23. A turbocharger, comprising: a variable turbine geometry having at least one or more guide vanes according to claim
 11. 24. The turbocharger according to claim 23, wherein at least one, more than one or all of said guide vanes of said variable turbine geometry have the same or a different shape. 